This invention pertains to surgical systems and, more particularly, apparatus and methods for attaching autologous or artificial tendon grafts to bone. The invention has application in, for example, repair of the anterior cruciate ligament (ACL) of the knee. It may also be used, for example, for repair of other ligaments, such as of the elbow or ankle.
It is not uncommon for ligaments and other soft tissue to tear or detach from bone. Athletes, for example, often suffer tears or other injuries to the anterior cruciate ligament, one of the ligaments connecting the femur. (thigh bone) and the tibia (shin bone) at the center of the knee joint. The ACL, which limits hyperextension of the knee and prevents the backward sliding of the femur on the tibial plateau, may be injured when the knee is twisted beyond the normal range of motion, e.g., when the knee is twisted while bending and weaving during skiing and other sports activities. ACL injuries may take the form of total or partial tears.
Reconstruction is the most common form of surgery for injuries to the ACL and involves replacing the ACL with a graft of autologous or artificial tendon. An autologous tendon graft may be “harvested” from the patient's patellar ligament, which is part of the common tendon of the quadriceps femoris, connecting the patella to the tibia. An alternative autologous tendon graft may be harvested from the semitendinosus tendon, which runs posteriorly and medially along the thigh and which connects the upper femur to the tibia.
Traditionally, patellar grafts are harvested with attached bone plugs that can be securely fixed at the ends of a bone tunnel drilled through the tibia and femur using a metallic interference screw, a metal screw and washer, or buttons. Drawbacks associated with the use of the patellar tendon-include difficulties in harvesting the tendon and postoperative complications.
More recent success has been achieved using one or more strands of the triple-stranded semitendinosus, tendon, which can be harvested with minimal-post-operative complications. The strands can be used alone or in combination with the gracilis tendon, which anatomically runs parallel along the thigh to the semitendinosus tendon. Although semitendinosus tendons are increasingly used in ACL repair, they are difficult to attach to bone, due in part to the absence of associated bone plugs.
The art suggests, several techniques for attaching the semitendinosus tendon to bone in ACL repair. One such technique involves suturing the tendon to a button or staple on the exterior of the bone. Drawbacks associated with this method include stretching or failure of the suture, which may be subjected to tensile forces ranging from 30-50 pounds.
Another technique involves attaching a tendon graft to bone using metallic screws. Although such metal screws demonstrate stable fixation and good tensile strength, they have, a number of drawbacks. These include distortion of post-operative radiological studies, an allergic or rejection reaction resulting from metal sensitivity associated with permanently implanted metal screws, and the potential need for additional operations for removal or replacement.
Another technique involves attaching a tendon graft to an anchor affixed within a tunnel drilled in the bone. One anchor intended for this use is the Mitek Ligament Anchor available from Mitek Surgical Products, Inc. That anchor includes prongs that lodge into the bone after the anchor has been pulled into position by a suture. A drawback of that anchor is that it must be lodged in the cortical layer near the surface of the femur and therefore necessitates the use of long tendon segments. In addition, the anchor's design necessitates that it be fabricated from metal to ensure sufficient holding strength.
An object of this invention is to provide improved surgical systems, and more particularly, improved methods and apparatus for attaching autologous or artificial tendon grafts to bone.
Another object of this invention is to provide improved methods and apparatus for attachment of autologous or artificial tendon grafts (e.g., for ACL repair) that are in which the attachment means can be fabricated from polymers or bioabsorbable materials, without the use of metals.
A related object of this invention is to provide methods and apparatus for attachment of autologous and artificial tendons that minimize or eliminate the risk of graft pullout normally associated with ACL or other reconstructive orthopedic surgery.